The Science of Coffee
The Science of Coffee is a documentary-style podcast that explores the microscopic science behind coffee to help listeners brew better at home. Host James Harper, a coffee professional and documentary maker, interviews leading coffee scientists worldwide. Topics include water chemistry, extraction, plant genetics, espresso technology, and sensory science. The show is a spin-off from Harper's podcast Filter Stories.
Episodes
Coffee Quality, Part 3: When the “quality” myth hits the farm
For twenty years, the 2004 cupping form profoundly shaped the specialty coffee world.
But on the hillsides of coffee farms, some of the form’s byproducts have been disadvantaging producers.
In this episode, we follow two producers whose lives collided with the myth of universal quality. These stories reveal how a single idea of “quality” can close doors for the people with the least power in
Coffee Quality, Part 2: How “quality” became a myth
If you ask two specialty professionals what makes a high-quality coffee, you’ll likely get a surprisingly consistent answer: clean, sweet, juicy, bright. To an outsider, they would be forgiven for thinking coffee quality is universally defined.
But the truth is more sober.
In this episode, we examine how a simple cupping form helped create a universal idea of quality. We then look at the evide
Coffee Quality, Part 1: The birth of specialty coffee flavours
For the longest time, coffees were dull and bitter. But then a small group of pioneers changed the world.
In this episode, we travel back to the 1960s and ’70s to meet the trailblazers who realised coffees could taste distinctive: sweeter, brighter, cleaner.
We discover how their personal preferences became a movement, then a form, and eventually a global definition of “quality”.
Please su
How specialty coffee woke up to water’s role in flavour
For the longest time, the coffee community only cared about water’s impact ruining espresso machine boilers and kettles. But what about water’s impact on coffee flavour?
In this episode, I tell the story of how the specialty coffee community came to understand water chemistry: the pioneering work of the computational chemist Christopher Hendon and British roaster Maxwell Colonna-Dashwood, the ge
The two ingredients in water that ruin your coffee, and the ancient story behind them
550 million years ago, earth was perfect. We had perfect water for coffee AND we were living in a vegetarian paradise!
But then Earth changed—violently. The planet shifted from a peaceful, plant-eating paradise to a darker, more brutal world. And in this new world, the chemistry of water was forever altered.
This is the wild story of how earth-shaking forces and the spirits of long-dead critt
Getting great water for coffee, step-by-step. Part 2: How to measure and treat your water
Water massively impacts your coffee’s flavours. But most of us struggle to fix our water because water science is confusing…
…until now! In this special collaboration with Lucia Solis (Making Coffee podcast), I guide her through the two most important concepts you need to understand to get great-tasting water for coffee: hardness and alkalinity.
We go step-by-step through:
• Why these concept
Getting great water for coffee, step-by-step. Part 1: Alkalinity, hardness and why it matters
Water massively impacts your coffee’s flavours. But most of us struggle to fix our water because water science is confusing…
…until now! In this special collaboration with Lucia Solis (Making Coffee podcast), I guide her through the two most important concepts you need to understand to get great-tasting water for coffee: hardness and alkalinity.
We go step-by-step through:
• Why these concept
Farm to port: why specialty costs more
Every time we open a bag of beautiful specialty coffee — like Erick Bravo’s from Finca El Chaferote in Huila, Colombia — we’re drinking something that’s been on a long journey.
And I mean long! Over 1500 kilometers north up and down the Andes mountain range, a distance more than twice the height of France.
Along the way, it passes through dozens of hands, machines, and decisions. We follow it
Why one Colombian farmer chose specialty, and the other walked away
I travel to Colombia’s Huila region to answer a question that’s puzzled me for years: if specialty coffee pays more, is better for the environment, and brews tastier cups—why don’t more farmers grow it?
I speak with two producers in the same region whose choices couldn’t be more different. One stakes his future on specialty. The other opts out.
Their decisions come down to more than passion or
The hard business of selling beautiful coffee, part 2
Volume. Cheap. Lame flavours. This is the traditional way of growing coffee in Brazil, and almost every farm does it this way.
But what if you wanted to produce beautiful, distinctive flavours instead—and make a living from it?
In this episode, we travel to Fazenda Paraíso in Minas Gerais, Brazil, where farmer Vicente Pereira and his daughter are on a steep learning curve finding buyers for t
The hard business of selling beautiful coffee, part 1
Volume. Cheap. Lame flavours. This is the traditional way of growing coffee in Brazil, and almost every farm does it this way.
But what if you wanted to produce beautiful, distinctive flavours instead—and make a living from it?
In this episode, we travel to Fazenda Paraíso in Minas Gerais, Brazil, where farmer Vicente Pereira and his daughter are on a steep learning curve finding buyers for t
The Speed of Heat: How to roast more coffee, faster!
To roast coffee faster, you need to turn up the heat….right?
No!
In this episode, we explore the three powerful methods of heat transfer that revolutionised roasting. We’ll journey from humble beginnings—when roasting three kilos took half an hour—to machines that now roast hundreds of kilos of coffee in the time it takes you to boil a kettle.
But beans roasted at lightning speed look stra
Coffee Roasting: How baby plant food transforms into delicious coffee flavours
A mother coffee plant gifts its baby everything it needs to grow—a green seed packed with food. But when we roast coffee, we hijack that gift and turn it into something else: flavor.
But what is flavor, at a microscopic level? What actually happens inside the bean when heat meets those nutrients?
In this episode, we shrink down to witness the Maillard reaction up close—a wild chain of molecula
Fruit juice or creamy almonds? Your guide to controlling cold brew flavors
When I started making cold brew this last year, I treated it like hot brew filter coffee. But no matter how I adjusted the grind or tweaked the brew time, I hardly got any differences in flavor…
Then it hit me: cold brew isn’t just a slower hot brew—it’s a completely different game with its own rules!
In this episode, I speak with leading coffee researchers who break down the microscopic dance
Hot vs Cold: The science behind temperature and taste
For years, I used cold brew as a last resort—the only brew method to tame dark, oily beans that were too bitter for hot water.
Then one day, I took a chance on a Guatemalan Gesha and brewed it cold. The result? A massive explosion of florals I’d never tasted before. That single cup sent opened my eyes into how extraordinary cold brew can be.
In this episode, I speak with world-leading coffee
Introducing: Season 3 of The Science of Coffee
We’re back with another series of The Science of Coffee—and this time we’re diving even deeper into coffee’s hidden microscopic secrets!
Over the past year, narrative audio producer and coffee professional James Harper has scoured academic journals, ventured deep into coffee farms, and conducted bold tasting experiments.
Now, he’s weaving those discoveries into captivating audio stories that r
Freshness and Grinding, Part 2: How grinders work deep inside
Deep inside your coffee grinder, tiny changes can have massive consequences.
This episode takes you deep inside Mahlkönig’s grinders to show you how coffee is ground and the importance of particle sizes on flavour.
If you’re a home coffee lover, you could easily spend thousands of dollars on your coffee grinder. But after diving deep into the R&D of grinder manufacturing, I learned that af
Freshness and Grinding, Part 1: Protecting your coffee’s flavours
For your coffee to taste its best, it’s crucial you buy fresh roasts and grind fresh.…
.….Or maybe not.
When I began creating this episode, I was convinced that ‘fresh is best’. But, after delving into the science of coffee freshness, I don’t believe that anymore.
This episode goes deep into how diffusion and oxidation changes a coffee’s flavours.
You’ll learn what it takes to store your coff
What Is Good Science? Part 2: How to think like a scientist
In the last episode, I discovered that rinsing my Chemex filter papers was a waste of time! As a result I’ve managed to claw back over seven days of my life left on earth.
But why stop there?
The coffee industry is full of elaborate ways of brewing and savouring coffee: fancy drippers, cold metal balls, “slurp-able” cupping spoons.
These are very fun, but how many of them actually affect the
What Is Good Science? Part 1: How to brew coffee like a scientist
Should you rinse your filter paper before making a filter coffee? Almost everybody in coffee internet says you should.
But what if most of coffee internet was wrong?
In this episode, I show you how I try to answer this question like a professional sensory scientist would.
It’s hard. It’s frustrating. But ultimately, it’s worth it because I end up saving seven days of my life left on earth!
Organic Coffee, Part 2: Why don’t we see more organic coffee farms?
Farming coffee organically is amazing because soils are more alive, birds and insects are more plentiful, farmers avoid getting sick with agrochemicals.
But, if it’s so great, why is less than 10% of the world’s coffee grown organically?
The fact is, going organic is hard. Much harder than growing coffee conventionally.
In this episode I show you the story of one of Central America’s most suc
Organic Coffee, Part 1: The magic of soil
The world’s farming soils are deteriorating quickly.
Conventional coffee farming where plants are grown using agrochemicals allowed farmers to reap huge harvests these last 70 years. But these agrochemicals have been at the expense of soil health.
I travel to Honduras to explore a potential solution: organic coffee farming.
Come with me as I show you the organic farming tricks of Don Rufino, o
Coffee Roasting, Part 2: Roasting made easy
Roasting coffee can be maddening. Just 4° Celsius is enough to make the same green beans taste distinctly different! And there are so many things roasters can play around with: temperature, time, fan speed, drum speed, types of probes…the list goes on and on.
So, if you want to start roasting yourself, where do you start!?
In the first half of this episode, I interview one of the world's leadin
Coffee Roasting, Part 1: How heat transforms coffee beans
What flavours do you want from your coffee?
Every coffee bean begins its life green. And if you brewed it up without first roasting it, you’d get a yellow-green cup of grass-flavoured water.
But, as soon you apply heat to a bean, the flavour can morph to from something quite vegetative to a very acidic unripe fruit, then a very sweet fruit, and eventually dark roasted flavours.
This is the magi
Smell and Taste, Part 2: Are you and I tasting the same flavours?
Ever wonder why you and your friends can taste the same coffee, but you can’t agree on the flavour notes?
Join me as I explore this metaphysical mystery! I speak with leading scientists and ask: are the flavour receptors in your nose and mouth the same as mine? How does music and the shape of a cup affect what we taste? What about our different cultural backgrounds and language?
Best of all, I
Smell and Taste, Part 1: How to be a better coffee taster
So you’ve just taken a sip of a very rare coffee, and flavours of passion fruit explode in your mouth.
But here’s the thing: that flavour of passion fruit is not coming from your mouth. It’s not even coming from your nostrils. It’s being picked up behind your eyes!
In this first episode of The Science of Coffee's second series, I unravel how our sense of smell and taste works to help you be a be
Introducing: Season 2 of The Science of Coffee
We’re back with another series of The Science of Coffee!
Across 10 science stories, narrative audio producer and coffee professional James Harper takes you on a journey into coffee's hidden microscopic secrets.
James has spent the last year traveling to Central America, Greece, Norway, Switzerland and interviewing dozens of the world’s leading coffee scientists. This insights will help you appr
6) Sonic Seasoning
Imagine you’ve got a cup of coffee in front of you. You haven’t tasted it yet. You therefore don’t know what it tastes like, right?
Wrong. Some scientists argue that you actually do know what it will taste like (more or less), and the act of tasting simply confirms what you have already imagined it will taste like. And that’s because a growing body of research is revealing that sight, sound and
5) Latte Foam
When was the last time you picked up a cappuccino with a mountain of foam perched on top? Maybe these are the cappuccinos you make every morning at home.
I personally really, really dislike them! The foam is cold, raspy, and gets in the way of the actual coffee liquid.
How much better would your mornings be if, instead, your cappuccino had that creamy, silky “microfoam” you find in a specialty c
4) Espresso Technology
A good espresso is a sublime experience: rich, sweet, and wonderfully caffeinated.
But, who woke up one morning and thought to themselves, ‘I’m going to build a contraption that forces a tiny amount of super hot water with incredible pressure through a bed of very finely ground coffee’?
Well, the fact is, the first “espresso” machine built 150 years ago was awful in almost every way. Worst of a
3) Plant Genetics
How can you make better coffee at home? Well, an easy way is to buy higher quality beans.
But, I’m concerned this is going to get harder and harder for you in the future.
Climate change is making coffee taste worse while also pushing farmers into financial hardship.
In this episode we explore how genetic development can produce a coffee tree that might save the day. Is there a wild coffee tr
2) Coffee Extraction
How you brew your coffee dramatically affects what you taste. And I do mean dramatic! Brewing up the same bag of coffee beans can taste like a slice of heaven, or a slap in the face.
So, what exactly is happening at a microscopic level when water swirls through coffee grinds? Why does boiling water extract certain flavours, while letting the kettle cool for five minutes make it taste markedly di
1) Water For Brewing Coffee
A newer, updated version of this episode is out — listen here instead!
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Water really matters when you’re brewing coffee. Different waters can dramatically change how a single coffee will taste.
But what is the right water for the best coffee?
In this episode I will give you the answer, but I will first take you back billions of years to tell you the story of a single mineral and how it's
Introducing: The Science of Coffee
The Science of Coffee is a journey into coffee's hidden microscopic secrets to help you make even better coffee at home.
Across six episodes, documentary maker and coffee professional James Harper takes you deep into the world of water for coffee, coffee extraction, plant genetics, espresso technology, latte foam and sonic seasoning.
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